Abstract: To prove the Bochi-Mané dichotomy for symplectic diffeomorphisms, it is used the idea of flexibility of split sequences when non dominance is verified. In this presentation we see how the non dominance is divided into four cases, what those cases represent and how can we prove that each type of split sequences is indeed flexible. This is of most importance to the general result since it is the flexibility property that allows to build the perturbations to obtain the generic property of the Mané original conjecture.